Morphine produces a variety of effects on a number of organ systems that are very species specific. For example, morphine causes constriction of the coronary arteries in dogs, whereas in our studies we determined that morphine produces a coronary vasodilation. The proposed studies will attempt to evaluate the effects of morphine on splanchnic blood volume. Splanchnic blood flow will be measured using the indocyanine green dye constant infusion technique and mean transit times across the splanchnic circulation will be measured with another indicator. Since we have demonstrated that morphine produces a splanchnic arteriolar dilation, the proposed studies will determine whether or not this leads to pooling of blood in the splanchnic capacitance vessels, as well.